Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02398579 2002-08-19
INTERMEDIATE VOICE AND DTMF DETECTOR DEVICE FOR IMPROVED
SPEECH RECOGNITION UTILIZATION AND PENETRATION
Field of the Invention
The present invention relates in general to voice recognition systems for
telephony,
and more specifically to a method and apparatus for providing voice and tone
detection prior
to allocation of a speech recognition engine to a call.
Background of the Invention
The integration of speech recognition into modern day PBX systems provides new
user interface capabilities to augment traditional telephone device DTMF tones
and 'feature'
keys for call control. Speech recognition capabilities may be provided through
the allocation
of speech recognition engines (SREs) to a call in progress. For example, PBX
systems
manufactured by Mitel Networks Corporation may be configured with a number of
ports for
allocating Speak@EaseTM SRE resources. Each SRE resource is a general purpose
"device"
which provides all speech recognition and related capabilities (which may be
composed of
one or more processes). These capabilities include, but are not limited to,
voice detection,
DTMF detection, voice recognition, and application processing.
As speech recognition becomes more common, it is anticipated that a much
larger
number of SRE resources will be required to accommodate increased utilization.
The
provisioning of additional SRE resources to meet anticipated usage increases
the overall cost
of a PBX installation. As a result, the potential penetration of speech
recognition applications
is subject to cost considerations and is limited except where cost justified.
According to the existing state-of the-art, SRE resources are associated with
a call
whenever there is a potential need for speech recognition, regardless of
whether speech
recognition is actually invoked during the call. Consequently, PBX systems are
now
configured with a plurality of SRE resources that are dedicated to servicing
one or more
speech recognition applications, in a PBX network. When all of the SRE
resources are in use,
subsequent requests for the supported speech recognition applications are
denied or deferred
CA 02398579 2002-08-19
until an SRE resource becomes available. When the SRE is servicing a user, all
capabilities
are provided, regardless of utilization. For example, if a user initiates a
request for which an
SRE is allocated and simply dials digits at the telephone device (i.e. dialing
the destination
number rather than speaking the name) then the full capabilities of the SRE
are underutilized.
However, as indicated above call control allocates the SRE resource whenever
speech
recognition may be required, regardless of actual utilization.
Summar~of the Invention
According to the present invention, a voice and DTMF detector resource (VDD)
is
allocated to a call prior to allocating an SRE resource. The SRE resource is
only allocated
when speech recognition capabilities are required. The Voice and DTMF detector
resource
(VDD) is a limited capability digital signal processor that can be provided in
volume at
relatively low cost (using existing Digital Signal Processing (DSP)
technology). The presence
or absence of the Voice and DTMF detector resource (VDD) does not impact the
SRE
resource.
Brief Descr~tion of the Detailed Drawing
A description of a preferred embodiment of the present invention is provided
herein
below with reference to the accompanying drawings in which:
Figure 1 is a block diagram of a telephony system incorporating a plurality of
intermediate Voice and DTMF detector resources (VDDs) and Speech Recognition
Engines
(SREs), according to the present invention; and
Figures 2 shows the structure and operation of a VDD in accordance with the
preferred embodiment.
Detailed Description of Preferred Embodiments
Turning to Figure 1, a telephony system is shown incorporating the principles
of the
present invention. Specifically, a plurality of telephones 1A, 1B, etc. are
provided for
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CA 02398579 2002-08-19
conducting telephone calls between parties under control of call control 3. In
accordance with
the present invention, a plurality of Voice and DTMF detector resources (VDDs)
SA, SB...SF
may be allocated to an originating call by call control 3 in a manner similar
to a traditional
DTMF receiver. Each VDD SA, SB, etc. is a special purpose digital signal
processing (DSP)
resource which provides DTMF detection, voice detection, voice buffering and
voice
streaming, as discussed in greater detail below. A plurality of SRE resources
7 is also
provided, as is known in the art.
In operation, call control 3 allocates a VDD (e.g. VDD SA) in response to one
of the
telephones (e.g. phone 1A) initially going off hook. The SRE resources 7 are
not immediately
allocated to the call, in contrast with prior art systems. Upon detection of
DTMF tone, the
VDD SA performs digit collection and reporting as is done by a traditional
DTMF receiver.
Upon detection of voice, however, the VDD SA provides an indication to call
control 3. Call
control 3 then allocates an SRE resource 7, establishes a connection between
the VDD SA
1 S and the SRE resource 7, and requests the VDD SA to begin streaming
buffered voice to the
connected SRE resource 7 (while buffering the received voice). The SRE
resource 7 receives
voice from the VDD SA as though connected directly to a telephone device and
performs the
usual speech recognition operations.
If an SRE resource 7 is unavailable, a warning is provided to the user by call
control
3. The user is prompted to be patient until an SRE resource 7 becomes
available or,
alternatively, to try their request later (i.e. defernng or rejecting the
request, respectively).
However, in the event that the VDD SA contains sufficient memory to buffer up
to ten
seconds of voice, (e.g. by applying real-time voice compression algorithms),
call control 3 is
configured to perform a second attempt to obtain an SRE resource 7 prior to
deferring or
rejecting the user request.
The VDD resource SA purges its voice buffer upon receipt of an instruction
from call
control 3.
Turning to Figure 2, the VDD consists of a DTMF receiver 10, a voice detector
12,
and optionally a narrow band frequency detector 14 to guard against spurious
triggers when
tones are present. The output of the detectors is fed to a decision logic
block 16 that
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CA 02398579 2002-08-19
determines whether a voice phrase or a DTMF tone is present. In parallel with
the foregoing
blocks, the voice is buffered in a voice buffer 18, to compensate for
latencies in the detection
process and delays in switching in the SRE resource.
The voice buffer 18 is continuously updated such that the newest sample
overwrites
the oldest. This can be implemented either by a circular buffer or a shift
register buffer, both
of which are commonly known in the art. The length of the buffer depends on
the inherent
latencies of the detectors, the delays in the system and the typical time the
user wishes to
allow for the system to respond.
Upon detection of a DTMF digit, the digit is reported to call control 3. When
voice is
detected, the delayed voice stream is switched at 20 to an SRE 7 for speech
recognition.
Additional speech recognition functions can be performed by the VDDs SA, SB,
etc.,
such as voice end-pointing and hot word spotting, in order to further off load
the
requirements of the SRE's 7.
Exemplary pseudo-code for implementation of the DTMF detector 10, is as
follows:
DO Forever
Receive Signal
IF DTMF detected
Send DTMF detected event to decision logic
END
ENDDO
Exemplary pseudo-code for implementation of the voice detector 12, is as
follows:
DO Forever
Receive Signal
IF Voice detected
Send Voice detected event to decision logic
END
ENDDO
Exemplary pseudo-code for implementation of the optional narrow-band frequency
detector, is as follows:
DO Forever
Receive Signal
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CA 02398579 2002-08-19
IF Narrow Band Freq detected
Send Narrow Band Freq detected event to decision logic
END
ENDDO
Exemplary pseudo-code for implementation of the decision logic 16, is as
follows:
DO Forever
IF DTMF detected
Send DTMF detected event to client
ELSE IF Narrow band freq detected (optional)
Do nothing
ELSE IF Voice detected
Send Voice detected event to client
END
ENDDO
A person of ordinary skill in the art will appreciate that by utilizing the
VDD
resources of the present invention, substantial savings may be obtained in the
cost of
deploying SRE resources. For example, in a networked telephone system having
1000 users
and allowing for 20% of the users to actively initiate call re-direction, 192
VDD resources
may be provided (6 banks X 32 VDDs per bank) for initial call allocation.
Allowing for 10%
of these calls to require actual speech recognition services, then 16 SRE
resources are needed.
The cost of 192 VDDs and 16 SREs is significantly less than the cost of 192
SRE resources.
It will be appreciated that, although embodiments of the invention have been
described and illustrated in detail, various changes and modifications may be
made. For
example, although the preferred embodiment utilizes a Mitel Speech Recognition
Engine
(sold under the name SpeakEasy or eak o asel, other SRE resources may be used.
Furthermore, the telephones 1A, 1B, etc. may be any suitable voice
communication device
such as a Plain Old Telephone Set (POTS), mobile phone, IP Phone, PC with
voice
communication functionality, etc. Also, the principles of the invention may be
applied to
other applications than speech recognition enhanced telephone directory
services. For
example, the invention may be used to advantage in a Call Center and/or
Interactive Voice
Response (IVR) application where a user may be prompted for information and
DTMF or
speech recognition is used to obtain caller responses. The invention as
described above has
been applied specifically to voice applications in the PBX domain. However,
the invention
may also be applied equally to voice applications in the CO domain and in
mixed media
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communications, in either domain. Specifically, the invention may be applied
to any situation
where a large number of general purpose SRE resources can be displaced by a
similar
number of low cost VDD resources and a smaller number of SRE resources.
All of the forgoing changes and modifications may be made without departing
from
the sphere and scope of the invention as defined by the claims appended
herein.
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